Adhesives vs. Mechanical Fasteners in MRO Applications

MRO engineers use a variety of mechanical fasteners across many industries from food production to aerospace manufacturing. Wherever machinery such as hydraulics, motors, turbines, compressors and engines need to be used and maintained, fasteners are used. However there are potential issues with mechanical fasteners that should be considered, especially as it relates to joining various substrates together in harsh and demanding environments.

Mechanical fasteners might not be the most sustainable or practical solution because they may limit material options and lead to material fatigue. Labor, material and processing costs may also increase as a result. When using mechanical fasteners such as bolts and screws, it is required to create a hole in both parts so the fastener component can be passed through. This method creates a route where contaminants can travel through and damages the structural integrity of the joined parts. In some circumstances, mechanical fasteners may require fixing plates to secure different materials.

Adhesives are becoming a cost effective and highly reliable alternative to mechanical fasteners. Additionally, they are often used in conjunction to create stronger and more reliable bonds.

Adhesives can also defray costs associated with drilling or tapping. They can be ideal in hazardous locations where mechanical fastening options may not be easily accessible or possible. Their use may help prevent vibrational loosening which is a large contributing factor to mechanical failure.

Adhesives are often the optimal choice when used to provide an inert barrier between likely corrosive metals or to set up a water-resistant barrier. They may also be designed to resist specific chemicals and can mitigate differential thermal expansion rates. Structural adhesives can distribute force over the entire bond area instead of just at the joining site. Consequently, adhesives work best when applied to large clean areas as stresses are spread out over the bonded surface area and are likely stronger than welding, rivets, or threaded assemblies in these cases.

A variety of MRO applications can benefit from adhesives. Anaerobic engineering adhesives are convenient adhesives that can cure at room temperature. There are many options that are not solvent based, so they are safer for workers and for the environment. Low-volatile organic compound and sustainable adhesives are also being developed to offer increasing environmental benefits.

While typically the longer the cure time the stronger the final bond, many adhesives reach fixture times in a few minutes. There are different curing options for adhesives as well, with some curing faster when exposed to high-intensity UV light. As a result, exposed edges can have a stronger bond while the remainder will cure anaerobically.

Process improvements may also make adhesives easier to use, for example, two-part/no-mix adhesives are available where the activator is sprayed onto a substrate before the adhesive.

Adhesives can be used to mount electrical panels, conduits and I&C equipment. In the oil industry, adhesives can even replace welding commonly used in petrochemical applications. Some other applications include:

• Gasketing - Anaerobic adhesives can replace pre-cut gaskets.
• Pipe sealing - Adhesive solution can be applied to gaps in connections and fittings to prevent leaks of fluids and gases.
• Retaining - Anaerobic adhesives can fill spaces between a variety of components.
• Threadlocking - Adhesives can be applied to mechanical fasteners to prevent loosening and corrosion. This will reduce the occurrences of failure and reduce the need to tighten bolts.

Additionally, MRO engineers are facing increasing pressure to incorporate sustainable practices in support of worldwide and national climate-change targets. Accordingly, MRO engineers are now more ready to consider alternative measures to traditional solutions. In an effort to reduce carbon footprints, engineering adhesives are being used to replace mechanical fasteners.

When using adhesives instead of mechanical fasteners, the number of tools and parts that are purchased can be reduced. This offers a reduction in transportation costs and storage. For instance, a single adhesive solution can be used to replace hundreds of washers. This reduces the energy, and fuel consumption in washer manufacturing, and transportation and storage requirements are reduced.

Adhesives can also be applied to MRO parts as a preventative measure. This can lead to reduced downtime and less need for replacement parts. Reducing downtime results in increased economic efficiency and reduces operating costs. Unsustainable side effects such as increased use of energy and resource can also be reduced with effective preventative maintenance.

Source: Engineering360